[linux-2.6-block.git] / arch / x86 / boot / compressed / aslr.c

#include "misc.h"

#ifdef CONFIG_RANDOMIZE_BASE
#include <asm/msr.h>
#include <asm/archrandom.h>
#include <asm/e820.h>

#define I8254_PORT_CONTROL	0x43
#define I8254_PORT_COUNTER0	0x40
#define I8254_CMD_READBACK	0xC0
#define I8254_SELECT_COUNTER0	0x02
#define I8254_STATUS_NOTREADY	0x40
static inline u16 i8254(void)
{
	u16 status, timer;

	do {
		outb(I8254_PORT_CONTROL,
		     I8254_CMD_READBACK | I8254_SELECT_COUNTER0);
		status = inb(I8254_PORT_COUNTER0);
		timer  = inb(I8254_PORT_COUNTER0);
		timer |= inb(I8254_PORT_COUNTER0) << 8;
	} while (status & I8254_STATUS_NOTREADY);

	return timer;
}

static unsigned long get_random_long(void)
{
	unsigned long random;

	if (has_cpuflag(X86_FEATURE_RDRAND)) {
		debug_putstr("KASLR using RDRAND...\n");
		if (rdrand_long(&random))
			return random;
	}

	if (has_cpuflag(X86_FEATURE_TSC)) {
		uint32_t raw;

		debug_putstr("KASLR using RDTSC...\n");
		rdtscl(raw);

		/* Only use the low bits of rdtsc. */
		random = raw & 0xffff;
	} else {
		debug_putstr("KASLR using i8254...\n");
		random = i8254();
	}

	/* Extend timer bits poorly... */
	random |= (random << 16);
#ifdef CONFIG_X86_64
	random |= (random << 32);
#endif
	return random;
}

struct mem_vector {
	unsigned long start;
	unsigned long size;
};

#define MEM_AVOID_MAX 5
struct mem_vector mem_avoid[MEM_AVOID_MAX];

static bool mem_contains(struct mem_vector *region, struct mem_vector *item)
{
	/* Item at least partially before region. */
	if (item->start < region->start)
		return false;
	/* Item at least partially after region. */
	if (item->start + item->size > region->start + region->size)
		return false;
	return true;
}

static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two)
{
	/* Item one is entirely before item two. */
	if (one->start + one->size <= two->start)
		return false;
	/* Item one is entirely after item two. */
	if (one->start >= two->start + two->size)
		return false;
	return true;
}

static void mem_avoid_init(unsigned long input, unsigned long input_size,
			   unsigned long output, unsigned long output_size)
{
	u64 initrd_start, initrd_size;
	u64 cmd_line, cmd_line_size;
	unsigned long unsafe, unsafe_len;
	char *ptr;

	/*
	 * Avoid the region that is unsafe to overlap during
	 * decompression (see calculations at top of misc.c).
	 */
	unsafe_len = (output_size >> 12) + 32768 + 18;
	unsafe = (unsigned long)input + input_size - unsafe_len;
	mem_avoid[0].start = unsafe;
	mem_avoid[0].size = unsafe_len;

	/* Avoid initrd. */
	initrd_start  = (u64)real_mode->ext_ramdisk_image << 32;
	initrd_start |= real_mode->hdr.ramdisk_image;
	initrd_size  = (u64)real_mode->ext_ramdisk_size << 32;
	initrd_size |= real_mode->hdr.ramdisk_size;
	mem_avoid[1].start = initrd_start;
	mem_avoid[1].size = initrd_size;

	/* Avoid kernel command line. */
	cmd_line  = (u64)real_mode->ext_cmd_line_ptr << 32;
	cmd_line |= real_mode->hdr.cmd_line_ptr;
	/* Calculate size of cmd_line. */
	ptr = (char *)(unsigned long)cmd_line;
	for (cmd_line_size = 0; ptr[cmd_line_size++]; )
		;
	mem_avoid[2].start = cmd_line;
	mem_avoid[2].size = cmd_line_size;

	/* Avoid heap memory. */
	mem_avoid[3].start = (unsigned long)free_mem_ptr;
	mem_avoid[3].size = BOOT_HEAP_SIZE;

	/* Avoid stack memory. */
	mem_avoid[4].start = (unsigned long)free_mem_end_ptr;
	mem_avoid[4].size = BOOT_STACK_SIZE;
}

/* Does this memory vector overlap a known avoided area? */
bool mem_avoid_overlap(struct mem_vector *img)
{
	int i;

	for (i = 0; i < MEM_AVOID_MAX; i++) {
		if (mem_overlaps(img, &mem_avoid[i]))
			return true;
	}

	return false;
}

unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET / CONFIG_PHYSICAL_ALIGN];
unsigned long slot_max = 0;

static void slots_append(unsigned long addr)
{
	/* Overflowing the slots list should be impossible. */
	if (slot_max >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
			CONFIG_PHYSICAL_ALIGN)
		return;

	slots[slot_max++] = addr;
}

static unsigned long slots_fetch_random(void)
{
	/* Handle case of no slots stored. */
	if (slot_max == 0)
		return 0;

	return slots[get_random_long() % slot_max];
}

static void process_e820_entry(struct e820entry *entry,
			       unsigned long minimum,
			       unsigned long image_size)
{
	struct mem_vector region, img;

	/* Skip non-RAM entries. */
	if (entry->type != E820_RAM)
		return;

	/* Ignore entries entirely above our maximum. */
	if (entry->addr >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
		return;

	/* Ignore entries entirely below our minimum. */
	if (entry->addr + entry->size < minimum)
		return;

	region.start = entry->addr;
	region.size = entry->size;

	/* Potentially raise address to minimum location. */
	if (region.start < minimum)
		region.start = minimum;

	/* Potentially raise address to meet alignment requirements. */
	region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);

	/* Did we raise the address above the bounds of this e820 region? */
	if (region.start > entry->addr + entry->size)
		return;

	/* Reduce size by any delta from the original address. */
	region.size -= region.start - entry->addr;

	/* Reduce maximum size to fit end of image within maximum limit. */
	if (region.start + region.size > CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
		region.size = CONFIG_RANDOMIZE_BASE_MAX_OFFSET - region.start;

	/* Walk each aligned slot and check for avoided areas. */
	for (img.start = region.start, img.size = image_size ;
	     mem_contains(&region, &img) ;
	     img.start += CONFIG_PHYSICAL_ALIGN) {
		if (mem_avoid_overlap(&img))
			continue;
		slots_append(img.start);
	}
}

static unsigned long find_random_addr(unsigned long minimum,
				      unsigned long size)
{
	int i;
	unsigned long addr;

	/* Make sure minimum is aligned. */
	minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);

	/* Verify potential e820 positions, appending to slots list. */
	for (i = 0; i < real_mode->e820_entries; i++) {
		process_e820_entry(&real_mode->e820_map[i], minimum, size);
	}

	return slots_fetch_random();
}

unsigned char *choose_kernel_location(unsigned char *input,
				      unsigned long input_size,
				      unsigned char *output,
				      unsigned long output_size)
{
	unsigned long choice = (unsigned long)output;
	unsigned long random;

	if (cmdline_find_option_bool("nokaslr")) {
		debug_putstr("KASLR disabled...\n");
		goto out;
	}

	/* Record the various known unsafe memory ranges. */
	mem_avoid_init((unsigned long)input, input_size,
		       (unsigned long)output, output_size);

	/* Walk e820 and find a random address. */
	random = find_random_addr(choice, output_size);
	if (!random) {
		debug_putstr("KASLR could not find suitable E820 region...\n");
		goto out;
	}

	/* Always enforce the minimum. */
	if (random < choice)
		goto out;

	choice = random;
out:
	return (unsigned char *)choice;
}

#endif /* CONFIG_RANDOMIZE_BASE */
Commit	Line	Data
8ab3820f KC	1	#include "misc.h"
	2
	3	#ifdef CONFIG_RANDOMIZE_BASE
5bfce5ef KC	4	#include <asm/msr.h>
5bfce5ef KC	5	#include <asm/archrandom.h>
82fa9637	6	#include <asm/e820.h>
5bfce5ef KC	7
	8	#define I8254_PORT_CONTROL 0x43
	9	#define I8254_PORT_COUNTER0 0x40
	10	#define I8254_CMD_READBACK 0xC0
	11	#define I8254_SELECT_COUNTER0 0x02
	12	#define I8254_STATUS_NOTREADY 0x40
	13	static inline u16 i8254(void)
	14	{
	15	u16 status, timer;
	16
	17	do {
	18	outb(I8254_PORT_CONTROL,
	19	I8254_CMD_READBACK \| I8254_SELECT_COUNTER0);
	20	status = inb(I8254_PORT_COUNTER0);
	21	timer = inb(I8254_PORT_COUNTER0);
	22	timer \|= inb(I8254_PORT_COUNTER0) << 8;
	23	} while (status & I8254_STATUS_NOTREADY);
	24
	25	return timer;
	26	}
	27
	28	static unsigned long get_random_long(void)
	29	{
	30	unsigned long random;
	31
	32	if (has_cpuflag(X86_FEATURE_RDRAND)) {
	33	debug_putstr("KASLR using RDRAND...\n");
	34	if (rdrand_long(&random))
	35	return random;
	36	}
	37
	38	if (has_cpuflag(X86_FEATURE_TSC)) {
	39	uint32_t raw;
	40
	41	debug_putstr("KASLR using RDTSC...\n");
	42	rdtscl(raw);
	43
	44	/* Only use the low bits of rdtsc. */
	45	random = raw & 0xffff;
	46	} else {
	47	debug_putstr("KASLR using i8254...\n");
	48	random = i8254();
	49	}
	50
	51	/* Extend timer bits poorly... */
	52	random \|= (random << 16);
	53	#ifdef CONFIG_X86_64
	54	random \|= (random << 32);
	55	#endif
	56	return random;
	57	}
8ab3820f	58
82fa9637 KC	59	struct mem_vector {
	60	unsigned long start;
	61	unsigned long size;
	62	};
	63
	64	#define MEM_AVOID_MAX 5
	65	struct mem_vector mem_avoid[MEM_AVOID_MAX];
	66
	67	static bool mem_contains(struct mem_vector region, struct mem_vector item)
	68	{
	69	/* Item at least partially before region. */
	70	if (item->start < region->start)
	71	return false;
	72	/* Item at least partially after region. */
	73	if (item->start + item->size > region->start + region->size)
	74	return false;
	75	return true;
	76	}
	77
	78	static bool mem_overlaps(struct mem_vector one, struct mem_vector two)
	79	{
	80	/* Item one is entirely before item two. */
	81	if (one->start + one->size <= two->start)
	82	return false;
	83	/* Item one is entirely after item two. */
	84	if (one->start >= two->start + two->size)
	85	return false;
	86	return true;
	87	}
	88
	89	static void mem_avoid_init(unsigned long input, unsigned long input_size,
	90	unsigned long output, unsigned long output_size)
	91	{
	92	u64 initrd_start, initrd_size;
	93	u64 cmd_line, cmd_line_size;
	94	unsigned long unsafe, unsafe_len;
	95	char *ptr;
	96
	97	/*
	98	* Avoid the region that is unsafe to overlap during
	99	* decompression (see calculations at top of misc.c).
	100	*/
	101	unsafe_len = (output_size >> 12) + 32768 + 18;
	102	unsafe = (unsigned long)input + input_size - unsafe_len;
	103	mem_avoid[0].start = unsafe;
	104	mem_avoid[0].size = unsafe_len;
	105
	106	/* Avoid initrd. */
	107	initrd_start = (u64)real_mode->ext_ramdisk_image << 32;
	108	initrd_start \|= real_mode->hdr.ramdisk_image;
	109	initrd_size = (u64)real_mode->ext_ramdisk_size << 32;
	110	initrd_size \|= real_mode->hdr.ramdisk_size;
	111	mem_avoid[1].start = initrd_start;
	112	mem_avoid[1].size = initrd_size;
	113
	114	/* Avoid kernel command line. */
	115	cmd_line = (u64)real_mode->ext_cmd_line_ptr << 32;
	116	cmd_line \|= real_mode->hdr.cmd_line_ptr;
	117	/* Calculate size of cmd_line. */
	118	ptr = (char *)(unsigned long)cmd_line;
	119	for (cmd_line_size = 0; ptr[cmd_line_size++]; )
	120	;
	121	mem_avoid[2].start = cmd_line;
	122	mem_avoid[2].size = cmd_line_size;
123
124	/* Avoid heap memory. */
125	mem_avoid[3].start = (unsigned long)free_mem_ptr;
126	mem_avoid[3].size = BOOT_HEAP_SIZE;
127
128	/* Avoid stack memory. */
129	mem_avoid[4].start = (unsigned long)free_mem_end_ptr;
130	mem_avoid[4].size = BOOT_STACK_SIZE;
131	}
132
133	/* Does this memory vector overlap a known avoided area? */
134	bool mem_avoid_overlap(struct mem_vector *img)
135	{
136	int i;
137
138	for (i = 0; i < MEM_AVOID_MAX; i++) {
139	if (mem_overlaps(img, &mem_avoid[i]))
140	return true;
141	}
142
143	return false;
144	}
145
146	unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET / CONFIG_PHYSICAL_ALIGN];
147	unsigned long slot_max = 0;
148
149	static void slots_append(unsigned long addr)
150	{
151	/* Overflowing the slots list should be impossible. */
152	if (slot_max >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
153	CONFIG_PHYSICAL_ALIGN)
154	return;
155
156	slots[slot_max++] = addr;
157	}
158
159	static unsigned long slots_fetch_random(void)
160	{
161	/* Handle case of no slots stored. */
162	if (slot_max == 0)
163	return 0;
164
165	return slots[get_random_long() % slot_max];
166	}
167
168	static void process_e820_entry(struct e820entry *entry,
169	unsigned long minimum,
170	unsigned long image_size)
171	{
172	struct mem_vector region, img;
173
174	/* Skip non-RAM entries. */
175	if (entry->type != E820_RAM)
176	return;
177
178	/* Ignore entries entirely above our maximum. */
179	if (entry->addr >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
180	return;
181
182	/* Ignore entries entirely below our minimum. */
183	if (entry->addr + entry->size < minimum)
184	return;
185
186	region.start = entry->addr;
187	region.size = entry->size;
188
189	/* Potentially raise address to minimum location. */
190	if (region.start < minimum)
191	region.start = minimum;
192
193	/* Potentially raise address to meet alignment requirements. */
194	region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
195
196	/* Did we raise the address above the bounds of this e820 region? */
197	if (region.start > entry->addr + entry->size)
198	return;
199
200	/* Reduce size by any delta from the original address. */
201	region.size -= region.start - entry->addr;
202
203	/* Reduce maximum size to fit end of image within maximum limit. */
204	if (region.start + region.size > CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
205	region.size = CONFIG_RANDOMIZE_BASE_MAX_OFFSET - region.start;
206
207	/* Walk each aligned slot and check for avoided areas. */
208	for (img.start = region.start, img.size = image_size ;
209	mem_contains(&region, &img) ;
210	img.start += CONFIG_PHYSICAL_ALIGN) {
211	if (mem_avoid_overlap(&img))
212	continue;
213	slots_append(img.start);
214	}
215	}
216
217	static unsigned long find_random_addr(unsigned long minimum,
218	unsigned long size)
219	{
220	int i;
221	unsigned long addr;
222
223	/* Make sure minimum is aligned. */
224	minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
225
226	/* Verify potential e820 positions, appending to slots list. */
227	for (i = 0; i < real_mode->e820_entries; i++) {
228	process_e820_entry(&real_mode->e820_map[i], minimum, size);
229	}
230
231	return slots_fetch_random();
232	}
233
8ab3820f KC	234	unsigned char choose_kernel_location(unsigned char input,
	235	unsigned long input_size,
	236	unsigned char *output,
	237	unsigned long output_size)
	238	{
	239	unsigned long choice = (unsigned long)output;
82fa9637	240	unsigned long random;
8ab3820f KC	241
	242	if (cmdline_find_option_bool("nokaslr")) {
	243	debug_putstr("KASLR disabled...\n");
	244	goto out;
	245	}
	246
82fa9637 KC	247	/* Record the various known unsafe memory ranges. */
	248	mem_avoid_init((unsigned long)input, input_size,
	249	(unsigned long)output, output_size);
	250
	251	/* Walk e820 and find a random address. */
	252	random = find_random_addr(choice, output_size);
	253	if (!random) {
	254	debug_putstr("KASLR could not find suitable E820 region...\n");
	255	goto out;
	256	}
	257
	258	/* Always enforce the minimum. */
	259	if (random < choice)
	260	goto out;
8ab3820f	261
82fa9637	262	choice = random;
8ab3820f KC	263	out:
	264	return (unsigned char *)choice;
	265	}
	266
	267	#endif /* CONFIG_RANDOMIZE_BASE */